A rotary encoder with built-in push switch, which is an embodiment of a prior art operation type electronic component with push switch, is described hereunder referring to FIGS. 9 through 13.
A prior art rotary encoder with built-in push switch comprises, as shown in FIG. 9 (cross sectional view) and FIG. 10 (partially cutaway top view), a movable member 1 affixed movable to a base board 2 in holding part 1C, a rotary contact wheel 3 attached revolvable on the movable member 1 and disposed at the middle part of the base board 2, and a switch 4 disposed at a rear part of base board 2 (at the right in FIGS. 9-10).
The rotary contact wheel 3 is provided at the bottom surface with contact plates 3A disposed in a radial arrangement for accepting contacts from elastic contact reeds 5 of the base board 2, and held revolvable at the central hole 3B by a pillar 1A of the movable member 1, with the top covered with an operating knob 6 that rotates together.
As shown in a perspective view of FIG. 11, the base board 2 comprises a hole 2A provided in a side part for holding the movable member 1 movable, a hollow 2C having a stop wall 2B for fixing the switch 4, elastic contact reeds 5 for generating electric signal by having contact with the bottom surface of rotary contact wheel 3, and terminals 7 for taking the generated electric signal out.
A coil spring 8, which is positioned by an extrusion 2D located on the base board 2 at a rear part, pushes a side of the movable member 1 in horizontal direction so that push rod 1B of the movable member 1 is usually kept off the switch 4. Switch 4 is, as shown in FIG. 9, fixed in the hollow 2C of base board 2 with the rear end touching to the stop wall 2B, and a button 4A facing to the push rod 1B of movable member 1.
The operation of the above prior art rotary encoder having push switch is described in the following.
The rotary contact wheel 3 rotates with the pillar 1A of movable member 1 as the axis when the knob 6 attached on the rotary contact wheel 3 is rotated by a force given in tangential direction indicated with an arrow F in FIG. 10. The radial contact plates 3A disposed on the bottom surface of rotary contact wheel 3 slide on the elastic contact reeds 5 of base board 2, and pulse signals are generated. The pulse signals are outputted through the terminals 7, thus it works as a rotary encoder.
While the operating knob 6 is being rotated, a pushing force is also given to the knob, but the spring force of said twisted coil spring 8 prevents the push rod 1B of movable member 1 from pushing the button 4A of switch 4.
When the operating knob 6 is pressed in the direction of an arrow G in FIG. 10 with more force than the force due to the coil spring 8, the entire part of the movable member 1 including the rotary contact wheel 3 is moved to the direction of an arrow H with the holding part 1C of movable member 1, or a hole 2A of the base board 2, as the axis of movement, causing the push rod 1B of movable member 1 push the button 4A to actuate the switch 4. As soon as the force given to the knob 6 is withdrawn, the force of twisted coil spring 8 pushes the movable member 1 back to the original position.
The above described prior art rotary encoder having push switch employs an independent completed switch for the switch 4 that works on a push of the operating knob 6, and comprises the coil spring 8 disposed at a rear part of the base board 2 for preventing the push rod 1B of movable member 1 from pushing the switch 4 while the operating knob 6 is being rotated, as well as for restoring the movable member 1 to the original position when the pushing operation on the operating knob 6 is finished. These result in a higher cost and an increased body size of a rotary encoder having push switch.
In the general trends towards the more compact and lower price of electronic appliances, those electronic components to be incorporated in such appliances are likewise requested to be compact yet have advanced functions, coming in low price. A means to meet the requirement is to make the components available on an automatic production line. A popular solution is introduction of an insert-shaping technique, wherein contact points, terminals and other conductive members are formed on a hoop of metal sheet to be inserted into a resin molded base board, for the later assembly on an automatic assembly machine.
Now in the following, a method of manufacturing a base board containing contacts, terminals and other conductive members is described with reference to FIG. 12, using the above mentioned prior art rotary encoder having push switch as the vehicle.
FIG. 12 illustrates a metal sheet hoop showing a set of conductive members formed on the metal sheet and a resin molded base board with the set of conductive members inserted therein. Numeral 9 denotes an electro-conductive metal sheet hoop provided with frame alley 9A, and 10 conductive members stamped in flat sheet form with each of the members remaining connected with the frame alley 9A at connecting sections 9B. Numeral 2 denotes a resin molded base board with the conductive members 10 inserted therein.
In the next step, the base board 2 undergoes a cutting at the joints 10A of conductive members 10, and then the conductive members 10 are formed to become elastic contact reeds 5. Then, the sections 9B connecting with the frame alley 9A are cut at cutting lines 9C, and the terminals 7 are bent downward to complete a base board 2 as shown in FIG. 11.
The cut surface 11 of electro-conductive metal sheet 9 is exposed out of the surface of base board 2 in the above prior art method. When a rotary encoder 12 having push switch 12 assembled with the above base board 2 is mounted on a circuit board 14 with a part of the operating knob 6 extruding out of outer casing 13, and the cut surface is positioned at a vicinity of the operating knob 6, a static electricity generated while the operating knob 6 is rotated with a finger discharges to the cut surface 11. The discharge affects the signals to be outputted from a rotary encoder having push switch 12, producing possible causes of erroneous operation of an apparatus.
In prior art methods, therefore, the cut surface 11 had to be covered with a separate metal board 15 electrically coupled with a ground sector 16 of apparatus by means of soldering etc., whenever there is a possibility of the electrostatic problem. This is a substantial drawback that results in an extra parts count and additional assembly steps.